The present invention relates to the technical field of fabrication of frames (stiles and rails) of doors and windows using hollow steel tubing, with a wall thickness of between 10 gauge and 16 gauge, where there is a requirement to control thermal conductivity between components inside and outside of a building.
The frames of conventional, thick walled, steel doors and windows are constructed from hollow tubes that may contain insulation within the hollow cavity of the tubing. This insulation controls both radiation and convection across the cavity but does not control conduction of heat through the steel walls of the tubes. Conduction of heat can cause significant energy loss and, in cold climates, doors and window frames can become very cold on the inside, causing problems of condensation and frosting. The present invention provides a means of providing a “thermal break” with an insulating material which separates inside and outside components from direct contact and effectively controls conduction.
Existing approaches teach that we may use two or more tubes separated by an insulating barrier to provide a thermal break. While such an arrangement limits conduction, the contact area is the full width of the tubing, which greatly reduces the effective insulating properties of the thermal break. Such an arrangement also uses much more steel than a conventional construction, increasing both cost and weight. Accordingly, these problems are overcome by the present invention which provides a means of adding a thermal break in thick walled tube construction that adds little weight and which utilizes the thermal properties of the insulating material to the greatest effect.
Although thermal breaks are common in the frames of aluminum windows and doors, the method and means of application requires the use of extruded profiles of aluminum that are not generally available in steel or, if available, would result in a structure far too heavy to be practicable. Some thermal breaks have been made using steel sheeting bent into complex folds that is only possible with steel thinner than 16 gauge. The present invention enables a thermal break to be provided in tubing constructed of carbon or stainless steel of between 10 gauge and 16 gauge.
The folded and extruded profiles currently used to create a thermal break can only be applied to straight sections of doors and windows and not to curved shapes such as a round window or an arched door or window. The present invention allows the thermal break to be utilized in the frames of square, rectangular, curved and or complex shaped doors and windows.